Many devices for converting bicycles into indoor exercise devices are on the market and still more have been patented or otherwise proposed. Those which support the bicycle in place all have, according to my observation, one or more deficiencies. Either they are expensive or difficult to set up or require modifications of the bicycle or lack stability or have more than one of the above limitations. There are other devices termed "bicycle rollers" which are simply what the term implies, sets of rollers on which the cyclist rides the bicycle and maintains his own balance. These require considerable skill on the part of the user.